1. Field of the Invention
The disclosure generally relates to a method for controlling a Bluetooth device, and more particularly, relates to a method for controlling a Bluetooth device for power conservation.
2. Description of the Related Art
A Bluetooth device may operate in two major states: a standby state and a connection state. Additionally, there are seven sub-states which are used to search devices or create connections, including page, page scan, inquiry, inquiry scan, master response, slave response, and inquiry response. For example, in the page scan, a slave listens for its own device access code for a duration of scan window; in the inquiry scan, the Bluetooth device is listening for inquiries from other devices for a duration of scan window. Furthermore, Bluetooth devices in the connection state can be in any of the four following modes: an active mode, a hold mode, a sniff mode, and a park mode. For example, in the active mode, a master and a slave participate actively on a channel by listening, transmitting or receiving the packets; in the sniff mode, a slave, rather than listening at every slot for messages from the master to the slave, sniffs only at specified time slots for the messages.
Generally, the Bluetooth device can save power when operating in the sleep mode. However, when it leaves or re-enters the sleep mode, some preparation work is required to be performed. Such preparation work will consume power and it would be a huge disadvantage if the Bluetooth device frequently leaves or re-enters the sleep mode and wastes its power on performing these preparation works.
FIG. 1 is a timing diagram of operations performed by Bluetooth devices of the prior art. As shown in FIG. 1, the Bluetooth device operates in sleep mode 107. When it leaves the sleep mode 107, it will first perform the wakeup preparation work 105, and then it will wake up to perform some connection operations 101 or 103, such as checking connection status or exchanging messages. After that, before it re-enters the sleep mode 107, it will perform the sleep preparation work 106. Since the Bluetooth device may frequently switch between the sleep mode and wakeup mode, the preparation work performed during the switch will consume a lot of power and shortens the life of a battery in the Bluetooth device.